SSH configuration file

notes

ssh

How to configure a remote host in the SSH config file

TL;DR

To add a new connection to the SSH config file (~/.ssh/config), open it and write the following:

Host [hostname_alias]
  HostName [hostname]
  User [username]
  #PubKeyAuthentication yes # If accessing via SSH
  #IdentityFile ~/.ssh/id_ed25519 # point to the private SSH key if available
  #OTHER_SSH_OPTION value # General format of SSH options

Then, from terminal, executing ssh [hostname_alias] will try to set a connection to the specified HostName using the specified User.

Breakdown

Each section starting with Host defines a connection. The lines below this statement define properties of the specific connection.
[hostname_alias] specifies an alias for the connection locally. Different aliases may specify the same HostName, e.g. to handle different users on a remote server.
HostName [hostname] specifies the target hostname. It can be an IP address (86.87.88.89) or a text string (github.com). In the first case no domain resolution is necessary. In the second, the internal /etc/hosts file will be queried and if no match is found a DNS query will be performed.
User [username] indicates the username to use in that SSH connection. If not not defined, it defaults to the current username.

A real example I use to connect to my home Raspberry Pi:

Host raspberry
  Hostname 192.168.X.Y
  PubKeyAuthentication yes #
  IdentityFile ~/.ssh/id_ed25519

Resources

Useful summary of SSH config file format and options.
Stackoverflow thread on the interaction between /etc/hosts and ~/.ssh/config.